Compositional evolution trace elements

Fractional crystallisation has been dominated by separation of various proportions of clinopyroxene and olivine in the mafic magmas, and of cli-nopyroxene and feldspars in the felsic melts. These generated decrease in ferromagnesian elements (FeO, MgO, Ni, Co, Cr, etc.) and increase in incompatible elements (e.g. Th, Ta, Nb, REE), with ongoing evolution. In contrast, ratios of incompatible trace elements were not affected by fractionation processes, and can be used to infer compositions of mantle-equilibrated melts. 

Barbieri M, Peccerillo A, Poli G, Tolomeo L (1988) Major, trace element and Sr isotopic composition of lavas from Vico volcano (Central Italy) and their evolution in an open system. Contrib Mineral Petrol 99 485-497... 

Many elements are present in the core at low-concentration levels (<1 wt.%). Some of the minor and trace elements may hold critical information on the origin, evolution, and current processes in the Earth s interior. A few examples are given below, where experimental data on minor and trace elements provide important constraints on the thermal state of the Earth, bulk Earth composition, and differentiation of the core. 

Kempton P. D., Fitton J. G., Hawkesworth C. J., and Ormerod D. S. (1991) Isotopic and trace element constraints on the composition and evolution of the lithosphere beneath the southwestern United States. J. Geophys. Res. 96, 13713-13735. 

If the model outlined above is valid, sihcic magmatism in the LFB involved net crustal growth, as juvenile mantle-derived liquids, or their differentiates were instrumental in the formation and compositional evolution of hornblende granites, and, to a lesser extent, the cordierite granites. The amount of new crust generated is estimated by determining the overall mantle component present within both granitic types, and this is best done isotopically, since the trace-element ratios are poorly constrained for the potential basaltic end-members. 

The overall consequence of the co-evolution of oxygenic photosynthesis and the redox state of the ocean is a relatively well-defined trace-element composition of the bulk phytoplankton. Analogous to Redfield s relationship between the macronutrients, trace-element analyses of phytoplankton reveals a relation for trace elements normahzed to cell phosphorus of (C125N16P1S13... 

Transport balance or box models have been used by many workers in the past in efforts to understand the trace element and isotope characteristics of the Earth s major silicate reservoirs, i.e. continental crust, and upper and lower mantle (e.g. Jacobsen Wasserburg 1979 Zartman Haines 1988). Although simple mass balance calculations can be applied to present-day trace element concentrations and Pb, Nd and Hf isotope compositions of major reservoirs, e.g. continental crust and depleted mantle, to test the hypothesis that these reservoirs are complementary, transport balance models are needed to test ideas on their evolution in time. The reason is that the isotope ratio variations are the result of time-integrated trace element variations in the reservoir, modified by fluxes between them. Below, recent transport balance models in which the evolution of the continental crust is examined using Th-U-Pb (Kramers T olstikhin 1997) and... 

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